Condenser transmitter



Jan. 1, 1929.

J. E. AIKEN CONDENSER TRANSMITTER Filed April 24, 1925 2 Sheets-Sheet 1 INVENTOR- 2? Josephf. Aiken WITNESSES:

AT'I ORNEY Jan. 1, 1929.

J E. AIKEN CONDENSER TRANSMITTER Filed April 24, 1925 2 Sheets sheet 2 WITNESSES: INVENTOR kfosep/z [.A/kep I S 0 I ATTORNEY .duce .a condenser transmitter containing Patented Jan. 1, 1929.

UNITED STATES.

PATENT OFFICE.

JOBEPH E. AIKEN, OF WILQINSBUSBG, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE I ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA. I I

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Application filed April 24,

v 15. Another object of my invention is to con structa condensertransmitter and an ampli fier combination which is suliiciently compact to 'be usable as a unitary device.

Another'objectof my invention isto pro-' 3 into electrical .vibrations, it has been customary to use a device containing, a diaphragm and a cooperating resistivemeans, the resistance of which is varied by the incidence of sound waves upon the diaphragm; Much difliculty has been experienced in obtaining a uniform response ofthe diaphragm andiment of my invention shownin Figs, land resistance unit to sound vibrations of simi-, I lar amplitude but of widelydiife'rent frequencies. It has been found extremely xiii-- for given amplitudes at low and high freq'uencies. This difficultyis caused largely by the natural resonance of thefdiaphragm and" the irregularities of the available resistance -1 materials. I v

My invention comprises a sound-sensitive device which properties other than the resistance of the circuit, are made responsive to sound vibrations. I have produced a construction in which I' employ a capacitance formed of asubstantial stationary plate and a tightly stretched elastic diaphragm form-- the other plate and positioned very close- 1925. Serial No. 25,596.

ly thereto and'subject to the inliuence of the sound to be translated. The influence of the sound varies the position of the diaphragm with respect to the stationary back plate and thereby produces a variation in. the-electrostatic capacitance therebetween. The varia tion in capacity is caused, by appropriate circuits, to influence the potential charge upon the grid of an ass'ociatedtriode amplifier and thereby to change the amount of current flowing .in' the plate circuit of the triode, thus translating sound vibration into electrical vibrations. i

My invention further contains means whereby a maximum effect upon the amplifier grid is obtained for a given, sound. intensity incident upon the diaphragm of the transmitter, and means whereby a compact vunitary device is constructed which is suit- .able for placement in conspicuous positions at' public assemblages. Other objects and structural details of my invention will be apparent from the follow ing description when read in connection with the accompanying drawing, wherein:

Figure 1 is a. View in front elevation of the casing of an embodiment ot my invention,

Fig.2 isa plan view of the apparatus constituting my invention with the cover of the device raised to expose the contents ofthe interior compartments,

Fig. 3 is a diagrammatic view of the apparatus and circuits of my invention,

Fi 4 is a view in vertical section along the line IV- IV of li'g. 2 of the embodi- 2, and.

40 ficult'to'obtain equal changes of resistance Referring to thedrawin s, my invention consists of a container 1 I aving compartments 2, 3 afid 4. A cover 5 having "a locking handle 6 permits access to the compartments 1 2, 3, and 4 and their contents. Compartment 1 3 contains the condenser transmitter 6 and resistors 7 and 8'. Com artment 2 contains the amplifier triode,!) which ismounted within and supported from a su'bcontainer 11 which has a sub cover 12. 'The sub-container 11 is supported within container 1 by felt pieces 14, 15 and 16 which serve as sound- .deadening-means. The triode 9 is supported 105 within the container 11 by elastic cords 17' and 18, cords .18 being threaded through a guide plate. 20.

- various circuits Within my device. The cable is passed through a collar 29 to which the wire braid shield 28 is soldered, and the lead wires are attached to the binding posts '22, 23, 24, 25 and 26. This cable is led to any suitable point. at which may be installed additional amplifiers through which the bincults are connected to transfer means early-- 1 ing the output currentsto the point of utilization. I My invention is particularly adapted as a sound translator adapted for the purposeaof modulating a radio broadcasting system. It may be connected to. and

caused to modulate any suitable radio broadcasting system. It is not, however, limited" to utilization with broad-casting apparatus ring 44, threa but may be einployed with any other apparatus which it is desired to energize by a translation of sound vibration into electrical vibrations. f A The condenser transmitter portion of my invention is placed in compartment 3 of the container 1. It is better shown in the detailed vertical section 1n Fig. 5. It comprises afoundation plate 31 to which is attached a sub-plate-32, upon which are mounted the resistors 7 and 8 and a condenser 33. Upon the foundation plate 31 is clamped a base ring 34 by means of a ring 35 suitably held by bolts 36 and 37, shown in Fig. 2. A clamping ring 39 .is attached to the base ring 34' by a plurality of screws 41 two of which are shown in Fig. 5. Between,rings 34 and 39 is clamped a diaphragm 42 which may preferably be made of highly tempered steel and may preferably be gold-plated. The opening of ring 34 is screw-threaded.

A pressure ring-43 is'inserted within the opening in ring 34 and brought into contact 1 with diaphragm 42. An additional thrust on ring 34, is inserted and tightly compressed against ring 43, thereby transmit-ting pressure through ring 43 to the diaphragm. Pressure applied in this manner causes a stretchin and tensioning of diaphragm 42 which raises its natural vibration frequency 60. of the diap ragm in this way,

.above audio to a very hi h value. This value may lie requency or may lie above the range of the usual vocal sounds.

By raisin the natural vibration frequency the majority of the sounds to which it will be called upon to respond, are sufiiciently low to be below.

its fundamental vibration frequency and it, therefore, shows no resonant response to them. Accordingly,it responds substantially proportionate to sounds of all frequencies ed similarly to the thread upconnected to the filament circuit of the triode below its natural period, thus causing no distortion such asis common to other types of v transmitters.

A ring of mica 45. is placed in contact with the stretched diaphragm upon the opposite side from ring 43; This mica ring serves as a spacer to position a carrying-ring 46. Attached to'ring 46 is a back plate 47 insulated from ring 46 by mica rings 48, 49 and 51. The rear end of back plate 47 is threaded 7 and the assembly is clamped together by a threaded nut 52 which is screwed down upon the mica rings 48, 49 and 51. Thering 46 is held in place by an auxiliary clamping ring 53 which is drawn into place by bolts 54. Protection is furnished the assembly by a cover plate 55. An auxiliary chamber 58 is formed in the back plate-47 and connection v is made from it to the rear side of the (as;

phragm 42 by a. hole 59; The foundation plate 31 is suitably clamped in place in .chamher 3 and separated therefrom by a felt packing 56 through which an opening is provided. A gauzc screen 57, while permitting the illgres s of sound vibrations, protects theopennected to condcnser'33 and throughresistance 7, which may have, a value ofabout '5. to 20 megohms, to the filament circuit of triode 9 and binding post 23. The other terminal of the condenser 33 is connected tothe back plate 47 of transmitter 6. The back plate 47 is further connected through a resistor- 8,

which may desirablyhave a value of 5 to 20 megohms to the terminal- 24, which, in

turn, is connected to the positive terminal of a B battery having desirably a potential :01 about 200 volts.

'The other terminal of the B battery is connected through the primarycoil of trans- 1 former 19 toterminal 24. The secondary of transformer 19 is connected to terminals-25 and 26 which,fin' turn, may be connected to other amplifying means. J

The transformer 19 has desirably a considerablestep-down ratio whereby the output voice frequency currents are delivered at a relatively low voltage and high amperage in order that the ratio of voice current to any currents that may be induced in the leads bp ad'acent power lines, may be as large as possib e, and thus the troublesomeefiects of attention.

- duction.

such induction minimized. There is required, of course, a correspondingly large step-up transformer as input means to the next ampllfier stage. The supply connections, and

output connections to other amplifier apparatus may be made through wires contained in cable 27 and protected by the braided cov-- ering 28. The metal braid 28, which is connected to the metal container 1 may also be used as one of the filament current leads by which arrangement-it serves as a round connection, further reducing the eiiects of in- \Vhen completely assembled and-Qt-he cover 5 of my device closed, it becomes an inconspicuous square boxhaving a. circular opening provided with a netting cover. The ex terior of the box may be finished in any desired way. When suitably' finis hed. it becomes a very inconspicuous object which may be in any desired manner. In the event that a translation of the soundsof a stage per'fiornian is desired, it may be hung from a cord ,nea the proscenium arch, for instance where it will not attract undesirable In the operation of my device, the filament of tr1ode'9 maybe energized by the application 'of a suitable low-voltage curposts 22 and 23 and the plate circuit of tri-v ode 9 may be energized by a higher voltage through resistor 8, which; however, is so source connected to the previously mentained filament circuit and to binding post 24, all through leads in'cable 27'. An electron stream from the filament of'thetriode 9 then makes possible a flow of current through the tube and through the primary coil of transformer 19. Simultaneously, the plates. of the vtransmitter are charged in opposite senses by the potential of the high voltage source,

great that the adjustment of voltage across the plates of the condenser takes place relatively slowly. The grid of cathode 9 then assumes a potential with respect to the cathode which is determined by the rate'of leakageof current through the resistor 7. Upon the. action of sound upon diaphragm 42, its spacing with respect tothe plate .47 is varied and thereby, the; capacitance between the plates is varied. The variation in capacitance causes a pulsating current to-flow'through' condenser '33 between the grid of triode 9 and the. condenser plate 7 of transmitter 6.

The'flow-ofsueh a fluctuating current causes changes in potential between the grid and the cathode of trio'de 9, which changel the electron stream therethrough and thereby change the plate current. The change in plate current induces a corresponding vibrating current-in the secondar of transformer 19 whichmay be delivered through terminals. 0 25 and '26, and the lead wires in cable 27 to the point of utilization thereof, which ma be an additional amplifier and a radio broa casting station. 7 c The variation in capacitance between the plates of transmitter 6 produced by incident sound is a relatively small proportion of the total capacitance between them for any but the very "loudest sounds. Also, additional capacitance is introduced by the capacitance between the connecting leads from the transmitter to the first amplifier stage. The" change in voltage upon the grid of the tri-- ode 9 produced by the influence of sounds upon the transmitter is proportional to the..

the change in the output current of t e amplifier will be. For this reason, it'i's highly .desirable that the parasitie'capcitance of the led wires be made as small .as possible; is only done by makingthe leads 'as'short as possible and placing them as far 'apart as possible. The construction of my device ac complishes both of these results and thereby secures a maximum signal current .output from the amplifier for a given sound intensity I incident upon the diaphragm. v

The careful sound-deadening in both compartments 2 and 3 reduces the magnitude of false vibrations produced by the effects of stray sounds directly upon triode 9.

By this means I have produced a soundse-nsitive translating means which inconspicuous in appearance,-which 1s umformly (responsive -.to sound waves over a wide rane of frequency, and which produces a su' I ciently large output of electrical vlbrations to be satisfactory for radio, broad-casting purposes and many-other purposes.

\ While I have shown only one embodiment of my invention in the accompanying drawings, it, is capable of various changes and modifications therefrom without departm from the spirit thereof, and ltis desire 0 therefore, that only such limitations shall be placed thereon as are imposed by the pr or; art or indicated inthe appendedclalms.

I claim as my invention 1. A sound-responsive a container having compartments, a condens er-transmitter positioned in; one of said compartments,'means of ingress-for sound thereto and sound-deadening'means thereabout, an amplifier trIode in another of said compartments, elastic supporting means 1 device comprising I i therefor, and sound-deadening means thereabout and an amplifying transformer in another of said compartments. J

2. A sound-responsive device comprising a pair of rings, a diaphragm therebetween, clamping means cooperating therewith, stretching means comprising a spacer ring having rounded edges, and a threaded pressure ringscrewed within one of said' pair of rings and affecting said diaphragm, and an lnsulatingly supported back piece, said diaphragm forming one element of a condenser,

. said back piece forming the other element,

said diaphragm being a apted to be moved by sound, thereby changing the capacitance of saidcondenser.

3. A sound-responsive device comprising a stretched vibratory diaphragm, a stationary member having a face parallel and ad jacentto said diaphragm, and supporting, positioning and insulating means cooperating therewith, said diaphragm and said member comprising an electrostatic condenser adapted to be varied in response to sound" waves, and-amplifying means comprising a triode space-current device, a current sup-" ply therefor and output means, the grid and cathode elements of said triode being respectively connected to said variable condenser,

and a container means comprising a plural compartment metalhc box and sound-intro ducing .and sound-deadening means therein surrounding said condenser and amplifier means.

4. A sound-responsive device comprising a multi-compartment container, a condensertransmitter disposed in one of said compartments, means of ingress forsound thereto,

5. A condenser transmitter comprising a diaphragm, means for tenslonmg said diaphragm, an electrode cooperating therewith,

and additional means for influencin the response of said diaphragm to Sean waves, said means comprising an adjustable closed chamber communicating with the space at the side of said diaphragm adjacent to which said electrode is positioned. I

In testimony whereof, I have hereunto subscribed my name this 13th day of April, 1925.

JOSEPH E. AIKEN. 

